Abstract Database

S-Wave Velocities Estimation Using Seismic Ambient Noise Analysis at San Miguel Volcano, El Salvador

Kevyn Enrique PINEDA ORTIZ
Supervisor: Takumi HAYASHIDA
Country: El Salvador

San Miguel volcano is one of the most active volcanoes in El Salvador. However, its structural properties are not fully understood. Four broadband seismometers were deployed by the Ministry of Environment of El Salvador from February 2014 to April 2014. We analyzed continuous ambient noise data (>0.2 Hz) using the spatial autocorrelation (SPAC) method and seismic interferometry technique, assuming the ambient noise is uniform both in time and space. The SPAC technique enabled us to obtain the phase velocity of surface waves from 0.2 to 1.0 Hz. We also determined Rayleigh-wave group velocities with seismic interferometry, which exploits Green's function from the cross-correlation of ambient noise recordings for each sensor-to-sensor pair. The combined use of the two methods offered ways to gain information about the shallow to deep seismic velocity structure from the same dataset. Through a joint inversion procedure, which included phase and group velocities, we estimated a velocity structure composed of four layers with shear wave velocities in the range of 1.0 km/s – 2.8 km/s. We located 15 volcano-tectonic earthquakes using the velocity model, resulting in a better-constrained hypocenter location. The hypocenter locations coincide with a deformation zone, known as the San Miguel Zone Fault, on the volcano's northern flank.

Keywords: SPAC method, Seismic Interferometry, Velocity structure, volcano